Among printed circuit boards (PCB) each mounting a BGA (Ball Grid Array) type integrated circuit (IC), there is a printed circuit board (PCB) in which a conductor layer and an interlayer insulating layer are alternately formed in multilayer. In the above-described multilayer printed circuit board (PCB), a number of vias for power supply and a number of vias for ground are arranged.
In a surface of the above-described multilayer PCB, a number of pads for balls to connect with array-shaped balls in the integrated circuit (IC) are also arranged. When the integrated circuit (IC) is mounted on the multilayer PCB, a number of pads for balls and a number of balls of the integrated circuit (IC) are connected. FIG. 6(1) shows a side view of a multilayer PCB 10 mounting an integrated circuit (IC) 50 made up of an IC chip 40, a package substrate 30, and balls 20. In FIG. 6(1), a surface of the multilayer PCB 10 is connected to a lower surface of the package substrate 30 through pads and balls 20.
Since integration in the BGA type integrated circuit (IC) has been advanced increasingly, the vias for power supply and the vias for ground in the one multilayer PCB have been increased in number more and more. Consequently, there arises a problem that in the multilayer PCB, undesirable induced electromotive forces are easily caused, which deteriorates reliability and electric characteristics of the integrated circuit (IC) and the multilayer PCB.
In order to solve the above-described problem, in a multilayer PCB disclosed in Patent Document 1, as shown in FIG. 6(2), vias for power supply 2 and vias for ground 6 are arranged in a grid shape. The grid-shaped arrangement as shown in FIG. 6(2) allows the induced electromotive forces caused by the vias in the multilayer PCB 10 to be mutually cancelled, and a mutual inductance between the individual vias becomes small, so that the reliability and the electric characteristics of the whole multilayer PCB 10 are improved.